Technical Field
The present disclosure relates to a display device and a module and a method of driving the display device.
Description of the Related Art
As a replacement for a conventional cathode ray tube, flat panel displays include a liquid crystal display, a field emission display, a plasma display panel, an organic light-emitting diode (OLED) display, and the like.
Among these displays, an OLED used in the OLED display has high luminance and low operating voltage characteristics. Since an OLED display is self-luminous, it has a high contrast ratio. Further, it is easy to implement an ultra-thin display with an OLED display. In addition, the OLED has a response time of several micro seconds (μs) and thus is suitable for representing moving images. Further, it has a wide viewing angle and can be driven stably even at a low temperature.
Pixels each including an OLED are arranged in a matrix in the OLED display. A data voltage corresponding to image data is applied to each of the pixels to flow a driving current at the OLED so that the OLED emits light at a desired luminance. Ideally, luminance of each of the pixels is uniform when an OLED display is driven. However, luminance among the pixels may become non-uniform due to deviations in electrical characteristic among driving transistors each in the respective pixels, deviations in cell driving voltages among the pixels, deviations in deterioration among the OLEDs each in the respective pixels, etc.
In particular, deviations in deterioration of the OLEDs cause an image sticking phenomenon that degrades the image quality of the OLED display.
There has been an approach for compensating for deviations in luminance among the pixels resulted from deviations in deterioration of the OLEDs. In this approach, compensation data is determined according to a cumulative amount of image data, the image data is compensated using the determined compensation data, the compensated image data is converted into a data voltage, and the data voltage is applied to a pixel.
FIG. 1 is a diagram illustrating a configuration of a conventional degradation compensation module 10.
Referring to FIG. 1, the conventional degradation compensation module 10 includes an image alignment unit 11, a memory 12, a look-up table 13, and a degradation compensation unit 14. The image alignment unit 11 corresponds and outputs image data DATA converted from an image signal to a size and a resolution of the display panel. The memory 12 stores a cumulative amount of data per each pixel in which the image data DATA applied to each pixel is accumulated at every frame. The look-up table 13 stores an average cumulative amount of data of the cumulative amount of data and compensation data corresponding to a cumulative driving time, which are mapped to each other.
The degradation compensation unit 14 reads out a decreased amount of luminance according to the cumulative amount of data per each pixel from the look-up table 13 with reference to the look-up table 13 and the memory 12. The degradation compensation unit 14 reads out compensation data Cdata according to the decreased amount of luminance per each pixel from the look-up table 13, and outputs compensated image data DATA′ by adding the compensation data Cdata to the image data DATA to each pixel. Thereafter, a data voltage corresponding to the compensated image data DATA′ is applied to each pixel so that each pixel emits light with its target luminance.
FIG. 2 is a graph illustrating luminance of a pixel L1 before the image data is compensated, the compensation data Cdata for compensating the image data, and luminance of a pixel L2 after the image data is compensated.
Referring to FIGS. 1 and 2, comparing luminance L1 a of a pixel section AR2 in which degradation occurs before the image data is compensated with luminance L1 b of each of pixel sections AR1 and AR3 in which degradation does not occur, a luminance difference of c is generated. As a result, an image streaking phenomenon may be generated at a boundary between the pixel section AR2 in which degradation occurs and the pixel sections AR1 and AR3 in which degradation does not occur.
To decrease the difference in luminance, the degradation compensation unit 14 sets the compensation data Cdata to b according to the decreased amount of luminance b of the pixel section AR2 in which degradation occurs with reference to the look-up table 13 and the memory 12. Thereafter, the degradation compensation unit 14 adds the set compensation data Cdata b to the image data DATA that is to be displayed at the pixel section AR2 in which degradation occurs, thereby outputting the compensated image data DATA′.
According to such a conventional compensation method, the compensated image data DATA′ is input to the pixel section AR2 in which degradation occurs so that the luminance L2 of the pixel section AR2 in which degradation occurs after the compensation is increased from a to c that is the difference in luminance before the compensation. As a result, the luminance L2 of the pixel section AR2 in which degradation occurs after the image data is compensated is the same the luminance L2 b of each of the pixel sections AR1 and AR3 in which degradation does not occur, such that there may be no luminance difference between the pixel section AR2 in which degradation occurs and the pixel sections AR1 and AR3 in which degradation does not occur.
However, according to such a conventional degradation compensation method, an amount of current corresponding to the compensation data Cdata flows continuously and additionally in a pixel in which degradation occurs. Because an amount of current flowing in the pixel in which degradation occurs is increased, degradation of the pixel may be accelerated as the conventional degradation compensation method is continuously performed.